The present invention relates to an adjusting gear in a motor vehicle, especially for a power seat adjustment, and to a method for assembling the same, which includes an essentially pot-shaped transmission housing in which the following elements are supported on a bearing shaft, starting from the pot bottom in the following sequence:
an output pinion member, PA1 a planet gear carrier non-rotatably connected with the output member and having at least two planet gears supported on bearing pins which mesh with internal circumferential teeth of the transmission housing, PA1 a sun gear also meshing with the planet gears, and PA1 a work gear non-rotatably connected with the sun gear which meshes with a work driven by a driving motor. PA1 the bearing shaft is pressed-in into the pot bottom, the output member together with the planetary gear carrier non-rotatably connected with the same is mounted over the bearing shaft in predetermined orientation, PA1 the planet gears are mounted in predetermined orientation on the bearing pins, PA1 the sun gear non-rotatably connected with the work gear is mounted in predetermined orientation on the bearing shaft and is connected with the transmission housing.
An adjusting gear or transmission of this type is disclosed in the DE-OS No. 33 22 863 (FIG. 3). The bearing shaft is formed in this prior art arrangement by axial projections 52, 54 which protrude on both sides from the pinion made in one piece with the planet gear carrier. The planet gears are preassembled on the planet gear carrier prior to the assembly whereby the bearing pins are provided with heads enlarged in diameter which fix the planet gears in the axial direction on the bearing pins. The assembly of this known adjusting gear is relatively costly because during the insertion of the planet gear carrier together with the planet gears, attention must be paid that all (for example, four) planet gears are properly oriented in order to come into engagement with the inner circumferential teeth of the transmission or gear housing and do not get stuck at the corresponding gear teeth. Similarly, during the subsequent installation of the sun gear, attention must be paid that the sun gear does not become stuck at the teeth of the planet gears but is able to come into engagement with the planet gears. The preassembly of the planet gears on the planet gear carrier lengthens the required assembly time.
By contrast, it is the object of the present invention to provide an adjusting gear of the aforementioned type which can be assembled in a more simple manner, especially with the aid of automatic assembly apparatus.
The underlying problems are solved according to the present invention in that the end face of the planet gears opposite the pot bottom are provided with at least one orienting surface for the oriented mounting on the bearing pins, in that the worm gear is provided on its end face opposite the pot bottom with at least one orienting surface for the oriented mounting on the bearing shaft, and in that the end face of the planet gears is provided with an abutment surface for the abutment at the backside of the worm gear disposed opposite the end face of the worm gear.
During the assembly of the adjusting gear or transmission according to the present invention, the transmission parts can be inserted sequentially into the transmission housing, namely, at first the planet gear carrier together with the output member in an orientation relative to the fixed transmission housing predetermined by the planet gear axes, thereafter the planet gears are inserted in an orientation predetermined by the orienting surfaces in such a manner that an immediate engagement of the individual planet gears in the inner circumferential teeth of the transmission housing is assured. Subsequently, the worm gear together with the sun gear non-rotatably connected with the same can be mounted in an orientation predetermined by the orienting surfaces in such a manner that the sun gear comes immediately into engagement with the individual planet gears. The axial fixing of the planet gears is now assured by way of the abutment surfaces of the planet gears which abut at the back side of the worm gear. These assembly steps can be carried out without any difficulties by an assembly robot. The preassembly of the planet gears can be dispensed with.
It is proposed that the end faces of the planet gears and/or of the work gear are proposed each with assemlby tool-engaging surfaces parallel to the bearing shaft axis. The assembly tool-engaging surfaces can be manufactured in a simple manner without impairing the shape of the abutment surfaces and enable that the respective part not only can be oriented at these engagement surfaces but can also be seized thereat.
The planet gears can be manufactured in a simple manner together with a low friction wear of the abutment surfaces at the worm gear if, according to another feature of the present invention, the planet gears are constructed with dead-end bores for the accommodation of the bearing pins, and the end faces are provided with a spherically shaped central area for the formation of the abutment surfaces.
The assembly of the adjusting gear is further facilitated according to the present invention, in that the bearing shaft is pressed into or riveted into the pot bottom of the transmission housing. In a first operating step, the bearing shaft is therefore inserted into the pot bottom of the transmission housing and then serves for the next following assembly steps as guidance for the parts to be mounted thereon.
The bearing shaft can be provided with a bearing collar which abuts, on the one hand, at the pot bottom of the transmission housing and, on the other, at the output member. The bearing collar therefore prevents a slipping-through of the bearing shaft during the pressing-in or riveting operation; additionally, it serves as axial counter-bearing for the output member, especially the pinion.
A pinion is preferably utilized as the output member which meshes with a toothed segment part or a toothed rack supported outside of the gear housing and entering into the gear housing through a corresponding aperture. However, for example, a cable drum could be used as an output member. The output member is preferably constructed in one piece with the planet gear carrier, preferably consisting of sintered metal. In the alternative, the output member and the planetary gear carrier can be inserted one within the other and riveted together with each other. The worm gear may be constructed in one piece with the sun gear so that a rotational bearing support of this part with a correspondingly large-area on the bearing shaft circumference results. The construction of the planetary gear carrier of sintered metal assures a high mechanical stability of the planetary gear carrier-support so that a proper inter-engagement of the teeth of sun gear and planet gears is assured with the possibility to make the planet gears as well as the worm gear together with sun gear of plastic material. The manufacturing costs of the mass-produced product adjusting gear in a motor vehicle are correspondingly reduced. This adjusting gear is preferredly used with a seat adjustment (longitudinal adjustment and inclination/height adjustment) even though the use of the adjusting gear for the back rest inclination adjustment is also possible, or in conjunction with a window lifter.
According to still another feature of the present invention, it is proposed that the output member, planetary gear carrier, sun gear and worm gear are rotatably supported on the bearing shaft, and that the end of the bearing shaft remote from the pot bottom is supported in a housing cover. In this manner the bearing shaft is supported at both ends. In order to preclude any possible axial play of the components mounted on the bearing shaft (for noise and wear reduction), it is proposed according to the present invention that a spring-elastic prestressing element, preferably a spring disk or spring washer, is inserted between the worm gear and the housing cover. This spring disk or washer can be inserted by an assembly robot.
In order to achieve as accurate as possible a centering of the bearing shaft inside of the transmission housing without any special expenditure, it is proposed according to the present invention that the housing cover be provided with at least one, preferably ring-shaped, positioning projection abutting at the inside of the transmission housing.
For an assembly-friendly rapid connection of the housing cover and transmission housing, it is additionally proposed according to the present invention that the housing cover is clasped together with the transmission housing.
The present invention also relates to a method for the assembly of the adjusting gear of the type described hereinabove, which is characterized in that
In order to avoid preassembly of the bearing pins on the planet gear carrier, it is further proposed that after mounting the planet gear carrier and prior to mounting the planet gears, the bearing pins be mounted on the planet gear carrier.